Effects of Monitoring Post Characteristics on Radiation Dose Measurements in Nuclear Emergencies

The radiation dose rates measured by continuous monitoring posts (MPs) are essential for understanding spatial dose rate distributions and determining appropriate radiation protection measures during a nuclear emergency. However, MPs have different characteristics, such as installation height, measurement units, and monitor types. We examined 1,692 MPs that are installed across Japan to investigate these characteristics. To quantitatively assess the effects of MP characteristics on radiation dose measurements, numerical simulations were conducted under assumed radionuclide distribution conditions following a light water reactor accident. The simulation model was validated through comparisons with observed monitoring data following the Fukushima Daiichi Nuclear Power Plant accident. The simulation results showed that the variability in measured values due to differences in installation height and measurement units generally ranged from 0.70 to 1.1 times when the ambient dose equivalent rate at a height of 1.0 m was used as reference. These findings provide important insights for the appropriate use of MP data and the improvement of emergency radiation monitoring systems in future nuclear accidents.